Counting on a new survey for woodland bats

Bat experts are trying to establish the best way to survey two woodland species in County Cavan.

The project by Bat Conservation Ireland (BCI) will help fill a shortfall in monitoring of both the Whiskered Bat and Natterer’s Bat.

Given their protected status, Irish authorities are legally obliged to monitor all nine of its bat species. However there’s no one size fits all approach available when it comes to counting different bat species.

“We have four different types of monitoring schemes catering for seven other bat species,” explains Dr Tina Aughney from Virginia who is leading the project. “The only two we are not able to monitor at the moment are the Natterer’s Bat and the Whiskered Bat.”

A modest grant of €8,500 from the Local Biodiversity Action Fund (LBAF) will help remedy that gap in data for the bats.

Each bat species has different ecological requirements which means they require individual methods of monitoring. For example the established technique to monitor Daubenton’s Bats is to undertake a waterway survey where volunteers walk a one kilometre transect along a river.

“They [Daubenton’s Bats] are very easy to identify along a river but in a woodland they are not easy to identify,” explains Tina. “And we don’t know where they are roosting, so we can’t do roost counts like we do for the Brown Long-eared Bat and the Lesser Horseshoe Bat.

“The reason we do roost counts for those two species is because you can’t hear them once they are out foraging because they have very quiet echo location calls, but they are very easy to count coming out of a roost.

“Each bat species has very particular needs and they are evolved to echo locate in certain ways, fly in certain ways, even come out in the evening in different ways and roost in different buildings.”

Through “trial and error” over the last few years BCI have earmarked two different types of survey for these woodland species: walking transects and static surveillance.

“Volunteers from Cavan Bat Group will be walking a specified 3.8km route with specialised equipment to see if the bats are present.

“We will also be putting up passive static surveillance detectors which record continuously through the night for a number of nights. We will compare the two and see which is the best way forward to monitor the bats.”

The surveys will be held at 10 sites in total, four of which are in County Cavan, namely Deerpark Forest Park Virginia, Dun a Rí Kingscourt, Castle Lough in Bailieborough and Killykeen Forest Park west of Cavan Town.

Tina is reasonably confident they will be found at each Cavan site. She has recorded both the Natterer’s and Whiskered Bats at Deerpark Forest, and a separate project documented the pair in Killykeen last year.

She believes sustainable bat monitoring has recently become more achievable due to technological advances.

“Bat surveys are very much dependent on bat technology and it’s come to the point where the equipment has become very good and it’s not as expensive as it was 10 years ago when we first started trying to see what we could do for these two species of bat.”

Tina laughs when the Celt notes that the Whiskered Bat and Natterer are ferocious looking animals:

“The whiskered bat is about the size of your thumb, it’s the smaller of the three myotis, and the Natterer is the size of your index finger - and while it may not be the prettiest, it’s a pretty cool bat to work with.”

Bats can’t take flight from ground level, however the agile Natterer’s Bat can snatch insects from the ground.

“While they can’t land and jump - they literally bounce onto the beetle in full flight and they can take spiders from their webs,” marvels Tina.

While no reliable, detailed data exists to examine the state of Irish populations of these woodland bats - known as myotis bats - a car-based survey which catered for the Leisler’s Bat and Pipistrelles indicates a decline in Natterer’s and Whiskered Bats.

“Incidental records through that scheme has shown there is a decrease in myotis. It’s triggered us to think: Ok we really have to start thinking seriously how we are going to monitor our last two species.”